I had the similar problem with spe 26 ,high voltage on ignition systems will find shortest route to ground ,is called "arcing " from the boot to the braided ground wire bypassing the spark plug , solved this by soldering a heavy wire to the ignition box & connecting it to the engine, it run perfect ever since . Sorry no photos ,sold 26cc ,moved to50cc. I was running an APC 17x8 on a 68 inch edge 540 , 10lbs it flue very well.